The transgenic and knockout mouse core will support the work of all 4 projects of the proposed PPG. The core will be located at the Rockefeller University Laboratory Animal Research Center. The core will: 1) micro- inject DNA into fertilized eggs to create transgenic mouse lines; 2) electroporate DNA constructions into ES cells, clone and select homologous recombinants, perform blastocyst injection of correctly targeted ES cells, breed chimeras to demonstrate germ line transmission to demonstrate germ line transmission of gene knockout; and 3) cryopreserve liens of transgenic and knockout mice.